Compositions containing thermosetting resins, such as epoxy resins, are widely used for electric and electronic parts since the cured products of such resin compositions excel in mechanical, electrical and chemical properties. Such resin compositions can be provided with increased flame retardancy to increase safety against fire.
One of the methods known for imparting flame retardancy to resin compositions has been to incorporate halogen-containing compounds, such as brominated epoxy resins, into the resin composition. Examples of such known methods are described in JP-A 2000-212249.
Halogen-containing compounds can impart a higher degree of flame retardancy to a resin composition than the resin composition alone. However, some halogenated compounds present additional concerns. Brominated aromatic compounds, for example, can release corrosive bromine and/or hydrogen bromide when pyrolyzed and can form highly toxic polybromodibenzofuran and polydibromobenzoxine when decomposed in the presence of oxygen. Furthermore, superannuated waste materials containing bromine are very difficult to dispose of. For these reasons, flame retardants that can be used instead of halogen-containing compounds would be desirable.
Methods employing phosphorus compounds, such as phosphine oxide compounds, have been used in flame-retardation techniques as alternatives to the use of halogen-containing compounds. Examples of such techniques are described in JP-A 2001-254001, JP-A 2004-067968, and JP-A H11-124489.
With methods employing phosphorus compounds instead of halogen-containing compounds, it is possible to circumvent the above problems caused by the use of halogen-containing compounds. However, depending upon the phosphorus compounds used, the resulting resin compositions can be unsatisfactory in terms of the chemical stability of the compositions during storage. Additionally, in some applications of the resin compositions, improvements in the characteristics other than flame retardancy, such as heat resistance and adhesion with copper foils or the like, may be of equal or greater importance.
Thus, it would be advantageous to provide solutions that can be readily implemented, such solutions directed to the above-related technical problems that can occur with the technology of flame-retardant resin compositions. It would be desirable for such solutions to provide increased flame retardancy but without the problems associated with the use of halogen-containing compounds. It would also be desirable for such solutions to provide a suitable storage stability of the resin compositions. Further, it would be advantageous to provide resin compositions suitable for use in the preparation of prepregs for laminates, which compositions exhibit desirable heat resistance and adhesion with various materials, for example metal foils (such as copper foils), as well as prepregs and laminates prepared therefrom. Additionally, it would be advantageous to provide flame retardants suitable for use in the preparation of resin compositions.